The present invention relates to an electrophotographic developing apparatus for a copier or a printer, and more particularly, to a liquid electrophotographic developing apparatus in which leakage of liquid developers is prevented.
Conventional liquid electrophotographic developing apparatuses bring a liquid developer into contact with an electrostatic latent image to be developed in any of several different ways. According to one method, the surface of a photoreceptor or other member carrying an electrostatic latent image is merely dipped into a bath of a liquid developer to develop the electrostatic latent image.
In another method, such as described in U.S. Pat. No. 5,017,968, a liquid developer is supplied to a head which extends across the width of a member bearing an electrostatic latent image and the liquid developer is supplied through one channel in the head to a slot opening where it is brought into contact with the surface of the image-bearing member. The liquid developer is then withdrawn from the slot opening through another channel in the developing head.
In a further liquid developing arrangement, as shown in U.S. Pat. No. 5,708,937, a rotating cylinder is coated with a liquid developer at a supply point and carries the developer into contact with the image-bearing member to develop the image. Other apparatuses for supplying a liquid developer to an image-bearing member through a slot extending across the width of the member are disclosed in U.S. Pat. Nos. 5,708,936, 5,737,672 and 5,765,078.
Such apparatuses for supplying a liquid developer to an image-bearing member have certain disadvantages including generation of odors resulting from vaporization of the liquid developer within the region of the developing unit, difficulties in reproducing colored images with successive developers of different colors in a single pass of the image-bearing member, and excessive size and cost of the developing units.
On the other hand, U.S. Pat. Nos. 5,358,659, 5,567,564 and 5,667,716 disclose methods of preparing magnetic liquid developers while U.S. Pat. No. 4,797,013 discloses the use of ferrofluids retained by magnets in gaps between moving members to seal lubricants in bearing arrangements. U.S. Pat. No. 4,645,960 discloses a ferrofluid bearing. U.S. Pat. No. 5,461,466 discloses a dripless seal for a liquid toner cartridge by which the cartridge is closed when not in use.
An object of the present invention is to set forth a liquid developing apparatus of electrostatic latent images that overcomes disadvantages of the prior art.
Another object of the present invention is to provide a liquid developing apparatus that minimizes emission of vapor from a liquid developer into the surrounding atmosphere.
A further object of the present invention is to provide a liquid developing apparatus that facilitates multicolor development of electrostatic images in a single pass of an image-bearing member.
An additional object of the present invention is to provide a compact and inexpensive liquid developing apparatus.
According to one aspect of the present invention, a liquid developing apparatus comprises:
a developing unit, having an elongated opening disposed adjacent to a moving image-bearing surface of a photoreceptor, for converting an electrostatic latent image into a toner image; and
an air duct, provided around the elongated opening of the developing unit, containing air flow therein having a predetermined air pressure to hold a liquid developer within a space between the developing unit and the image-bearing surface while permitting toner particles in the liquid developer deposited on the image-bearing surface to be retained by the image-bearing surface and allowing volatile solvent in the developer to be vaporized into the surrounding atmosphere.
According to another aspect of the present invention, a liquid developing apparatus comprises:
a plurality of developing units, each having an elongated opening disposed adjacent to a moving image-bearing surface of a photoreceptor which passes adjacent to the plurality of developing units in succession, for converting an electrostatic latent image into a toner image, each of the plurality of developing units containing a liquid developer of a different color; and
a plurality of air ducts, each provided around the elongated opening of the developing unit, containing air flow therein having a predetermined air pressure, for causing the liquid developer to be retained adjacent to the elongated opening in the developing unit while depositing toner particles on an electrostatic latent image on the image-bearing surface of the photoreceptor as the photoreceptor moves adjacent to the elongated opening.